[pappy, jakesdad,Bradley300] - ATV Riders Forums - Honda, Yamaha, Suzuki, Kawasaki, Polaris, CanAm, Arctic Cat, Kymco ATVs

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pappy, jakesdad,Bradley300
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Posted by: RAPTORPIT

I am new to this site, and am curious if one of you two have heard, about a 4 valve head for the Rap 250.
I stumbled across it on another forum, which i believe i have seen you guys post there allso.
I believe is was over seas in England, a member there was talking about it?
The reason i bring it up is i can,t find that forum again. I would appreciate any help. I would like to get my hands on that 4 valve head!!
Thanks Raptorpit

Posted by: jaksdad

hi
I think you need to look closer to home, I am led to believe Duncan Racing may be the leaders in this one. We are told over here (rumours) that one is being tried now, I don't know, can only speculate but have been told by leading U.K Yamaha dealer that Duncan Racing are producing something.
Unless, someone can tell us different ??

Posted by: RAPTORPIT

jaksdad, thanks for the help. I called duncan racing they are not going to make a 4 valve head. He did say he can make just as much power out of a 2 valve head. The owner allso said he has ready to ship 12-1 comp pistions and a few different big bore packages avaiable now. The next couple of weeks he will have a cam avaiable, plus larger valves and seats springs. he allready has a pipe and a filter set up allso. I hope this helps every one.
Thanks again to jaksdad for the help. RP

Posted by: jaksdad

Thanks.
I had been told that the 4 valve head wouldn't create that much more power and as you were told a cam would make a vast difference. At the moment we cannot do anything to our engines with club rules so we are just taking note as to what is coming out, seeing what can be done without modifying the engine, i.e c.d.i, etc. We already have the GYTR exhaust and Filter kit, just trying the same on another quad but with the UNI filter.
Still, keep you informed if we hear anything good over here.

Posted by: RAPTORPIT

Thanks,
Just wondering if you like the gytr pipe and filter. I have heard it really makes a huge difference, when jetted allso?

Posted by: Pappy

I had heard the same as you all have posted. We opted to just run a stock piped and jetted combo to see what was going to be available and to see what worked before we opened up the engine.

Posted by: jaksdad

the full GYTR system is excellent quality, nice looking too, it just helps the system get it out, only noticed slight power increase but have not done a comparison yet on a dyno, we will know then for definite. Scorpion, Doma etc all have systems too, still waiting to get on a dyno, all we have done is fitted a 140 main jet instead of the standard , seems o.k.
Got 4 Raptor 250's here at the moment in all states of build, but, all with LoneStar arms, couple with LoneStar +1",+2" steering stems & Streamline Steering Dampers, but standard swing arms, don't see the advantage of the +1" at the moment,Peps Front Shockers (Long Travel) on 2 standard on 2. As this is a learning time for the kids now they have come off the autos, just taking things easy for the start of the season as they learn the differing power available with the 4 stroke.

Posted by: bradley300

you probably saw that on project blaster's forums ( www.projectblaster.com ) diamond racing said they are working on one, also my sponsor SMS and GT Thunder may work together to build one, but i'm not sure yet

Posted by: raptor684

I finally got my daughters jetting close last weekend and it seems to be running alot better from the test runs. Would still like to change the pilot jet again though. I think the raptor 250 with the GYTR pipe on it sounds better than my z400 with the FMF on it.